Railway signaling system



A. HUFNAGEL Filed sept. 9, '1943 Aug. 8, 1944.

' RAILWAY SIGNALING SYSTEM Patented Aug. 8, 1944 Andrew Hufnagel, Wilkinsburg, Pa., assignor to The Union Switch Yr-Signal Company, Swissvale, la., a corporation of `Pennsylvania Application September 9, 1943, Serial No.7501,640

8 Claims.

My invention relates to a railway signaling system of the type employing. coded energy in the track circuits thereof, and particularly to an improvement in the system shown in an application for Letters Patent of the United States Serial No. 452,894 of Frank H. Nicholson and Crawford E. Staples, now Patent No. 2,331,134 dated October 5, 1943.

In that application there is shown a five indication signaling system employing a timing unit of the type shown in an application for Letters Patent of the United States Serial No. 452,902 of Carl Volz to detect the presence of energy of 75M code frequency in the rails of a track section.

The code following track relays available for use in systems of this type are equipped with four movable contacts and it is necessary to arrange the circuits governed by the track relay so that this number of contacts will be sufficient.

In the system shown in the application of Nicholson and Staples energy is supplied to the primary winding of the decoding transformer and to the timing unit over circuits controlled by the same front contact of the track relay. This joint use of the track relay contact saves a contact, but it has been found that the decoding transformer interferes with the timing unit and makes it difcult to secure the desired operation from the timing unit.

In addition, in the system shown in the application of Nicholson and Staples, the relays HB and BSA are energized in series during the long on,

periods in the 75M code to thereby prevent release of the contacts of relay BSA and resu-ltant interference with the supply of energy-to the adjacent section in the rear at such times.

Because of the resistance of the winding of relay BSA, it has been found to be difficult to supply sufcient energy to relay HB during one long on period in the '75M code to insure that the relay will remain picked up during the intervals between such long on periods.

An object of this invention is to provide an improved system of the type described which is arranged so'that the timing unit is energized over a circuit which, during the periods in which energy supplied to the timing unit, is employed only for this purpose to thereby insure that this unit will function reliably.

A further object of the invention is to provide improved means for controlling the relays BSAl and HB in a system of the type described.

Another object of my invention is to provide a system of the type described and incorporating improved means for energizing the relay BSA during the long on periods in the '75M code Without affecting operation of the relay at other times.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawing.

I shall describe one form of railway signaling system embodying. my invention, and 'shall then point out the novel features thereof in claims.

In the drawing,

Fig. l'is a diagramshowing a section of railway track equipped with one form of signaling appa` ratus embodying my invention, and

Fig. 2 is a diagram of the modied coded energy employed in this system.

Referring to Fig.'1 of the drawing, there is showntherein a stretch of 'railroad track over Which traffic normally moves in the direction indicated by the arrow, that is, from left to right. The track rails I and 2 `of the track stretch are divided byinsulated joints 3 into track sections for signaling purposes.

Electric current may be employed for propulsion purposes and where this is so alternating current energy isv employed inthe track circuits, and impedance bonds 4 ofthe customary form are provided to conduct the propulsion current around each pair of insulated rail joints. As the description proceeds, however, it will be apparent that the apparatus of this invention is equally well suited for use von a steam road in which direct or alternating current may be employedin the track circuits, while the impedance bonds may be omitted.

In addition, .as impedance bonds are employed the signaling apparatus includes means to check the insulated joints. As here shown, this means is the non-cascading lockout circuit of -Letters Patent of kthe United- States No. 2,235,134 issued March 18,` 1941 to Leslie R. Allison and Frank H. Nicholson, If this invention is employed in a track stretch where impedance bonds are not required, the portions of the signaling apparatus relating to the lockout circuit may be omitted.

Similarly, the decoding means provided by this invention for detecting the modied 75 code is not limited to use in wayside apparatus .but may be v incorporated in cab signal apparatus for use on adjoining sections HT and I 3T, are shown. Eachv of these sections has located at the entrance end thereof a signal S for governing traffic in the track stretch. The signals illustrated are of the Oy former IEDT, and a timing unit iZTU, while each familiar colo-r light type and each signal has an upper and a lower portion each of which has a green, a yellow and a red lamp. The invention, however, is not limited to the use of signals of this type and any appropriate form of signal may be used. Likewise, the invention is not limited to a system employing wayside signals, but is equally applicable to track stretches without wayside signals and having provision for cab signals only.

The rails of each track section form a part of a track circuit to which coded alternating current signal control energy is supplied at the exit or leaving end from the secondary of a track transformer TT. The alternating current supplied to the track circuits is derived from a suitable sourceand may he distributed throughout the trackA stretch by a transmission line, not shown. The terminals of the power supply source are designated BX and CX, and it will be assumed that the energy suppliedV from this source isv alternating current of a frequency of 60 cycles per second.

The signaling system shown in Fig. l makes use of track circuit energy coded at four different frequencies. This coded energy is provided by code transmitters CT which interrupt the supply circuits for the associated track transformersa definiteinum-ber of times per minute according` to trallc'or-o-ther'conditions ahead. As shown, each code transmitter is provided with fourV circuit making and breaking contacts which are continuously actuated by av motor or other suitable mechanism. The rate of operation of the contacts 15, IRQ and' l8 i'sY such` as to provide 75, 120 and 180A energy pulses per minute,l respectively, which are separated by periodsv of equal 'duration in which nov energy i's supplied'.

Each codetransmitter hasanother contact designated M which is so operated as tol produce two cycles of coded energy of-'75' code frequency in whichI rthe'y on and' olf periods are of approximately equal duration, while every third code cycle is modified in such manner that the off period is much shorter than normal and the length of the on period is correspondingly increased; The pattern of this code is shown in Fig. 2'. Since the distinguishing characteristic of the '75M code occurs in 'every third code cycle of the 75 code, the 75M'code is in effect energy'of '75 code frequency modulated 25 timesl a minute.

The details of construction of the code trans- -rectifier unit IZRU. This unit includes a transformer, a capacitor and a. reactor so arranged and proportioned as to freely pass 6G cycle signal control energy but so as not to passV propulsion current of a different frequency. The unit RU includes; in addition, a rectifier which converts: into direct current the alternating current supplied through the unit. 0

The signal I2S has associated therewitha track relay i2TR, auxiliary relaysiZFSA, IZBSA, IZHA, IZHB, HK, |2J and IZTRB, a decoding transof the other signals in the track stretch has assoelated therewith equipment corresponding to that associated with signal I2S.

Each signal also has associated therewith a source of direct current, such as a storage battery, not shown, the terminals of which are designated B and C.

The system provided by this invention is similar to that shown in the application Serial No. 452,894 of Frank H. Nicholson and Crawford E. Staples, but differs therefrom in the manner of supplying energy to the relay HA, to the holding winding of relay FSA, to the timing unit TU, and for energia ing the relays HB and BSA when energy of '75M code frequency is supplied to the track relay.

The equipment is shown in the condition which it assumes when the track stretch is vacant, At such times energy of 180 code frequency is supplied to the track transformer |2TT by the equip ment associated with section IST. The equip-- ment for section ir3T operates in the same manner as that for section IZT.

The coded energy supplied to l,track transformer lTT feeds to the track; relay |2TR and produces code following operation of this-relay. As a result of operation of thev relay I2TR, energy alternately supplied to the two portions of the primary' 20 of transformer |2DT from the direct current source. During the picked-upv periods of the track relay contacts energy is supplied from the transformer secondary winding' ZZ to the pick-up winding of the relay l ZFSA over the cir' cuit established by the` track relay contact I6, while during the released periods of the track relay its contact i6 establishes a snubbng circuit for the relay 2FSA to keep the contacts ofthe latter relay picked up during the off periods in the code.

When the track relay contacts are released,

energy isy supplied to the relay IZBSA over a' circuit which includes back contact H of the track relay and front contact 2S of theY relay lLJFSA, while contact 25 also connects a snulobing' resistor t! across the terminals of the winding of relay MESA to make it slow in'releasing.

At this time the relay IZHA is energized 'hy currentsupplied over its stick circuit which isl traced from terminal B through its own front contact 29, front contact 3B of relay I2BSA,. winding of relay |2H'A. and back contact 45 of relay iZTRB to terminal C. A resistor 32 is connected across the terminals of the winding vof relay EZHA to make the relay slow to release.

The relays I2K and |2J' are energized from the` decoding transformer through resonant units IZUDU and IDU, respectively, which include. inductances and capacitances arranged and proportioned to permit energy to flow freely through the units when the frequency of the current supplied thereto is that which is present when the track relay is responding to energy of and code frequency, respectively,`and to substantially prevent flow of energy at other times. Each of these units also includes a rectifier for reati-I fying the energy supplied through the unit.

As the track relay is responding to energy of, 180 code frequency, energy is supplied through the unit I SUDU to relay I2J and its contacts are picked up. Accordingly, Contact interrupts the circuit through` supplied to the timing unit energy is not supplied from this unit to the relay which energy. is

|2TRB and its contacts remain released so that.

the contacts of relay IZHB also remain released.

32 of relay HIJ` IZTU, and as a resultv As relays I2I-1A and I2J are picked p,fenergy is supplied to the upper green lamp Got signal IZS over a circuit which includes frontcontact 34 of relay I2HA and front contact 35'of relay I2J, while energy is supplied to the lower red lamp R of this signal over a circuit which includes front contact 3E of relay IZHA and front contact 38 of relay I2J. Accordingly, the signal I2S displays a green over a red light which Yis'its clear or least restrictive indication.

At this time energy of 180 code frequency-is supplied to track transformer II'I'I over a circuit Which is traced from terminal BX through contact |80 of the the code transmitter I ZCT, front contact 4D of relay I2J, front-contact `42 of relay I2HA, front contact 43 of relay I ZBSA, front contact 44 of relay I2FSA, and the primary winding of the track transformer II'II to terminal CX. Accordingly, energy of 180 code irequency is supplied to the rails of section I IT and the signal for that section is caused to display its clear indication.

When a train moving in the normal direction of traflic enters section I2T, the track relay I2TR` is shunted and relay I 2FSA releases so thati'ts contact 26 interrupts the supply of energy torelay IZBSA and also interrupts the snubbing circuit for this relay, with the result that relay I2BSA quickly releases. On release of relay IZBSA its contact 30 interrupts the circuit of relay IZHA, While when'the track relay ceases to follow code, energy is no longer supplied to relay |2J and its contacts release. v

As a result of release of the relays IZHA and I2J, the circuit of the upper green lamp G of signal I2S is interrupted, and the upper red lamp R is lighted by current supplied over backlcontact 34 of relay I2HA; also the circuit traced above for the lower red lamp R is interrupted and this lamp is lighted by energy supplied over back contact 36 of relay I2HA. The signal now displays a red lamp over a red lamp which is its stop or most restrictive indication.

At this time energy of '75 code frequency is supplied to the track transformer I ITT over a circuit Which is traced from terminal BX through back contact 43 of relay I2BSA, back contact 44 of relay IZFSA, and contact 'I5 of the code transmitter I2CT.

When the train enters section IST, the equipment for that section operates in thesame manner as the equipment for section I 2T so that signal ISS provides its stop indication, while energy of 75 lcode frequency is supplied to the track transformer I2'I'I'.

When the train vacates section I2T, coded energy feeds to the track relay IZTR, and on the first movement of the track relay contacts to their picked-up position an impulse of energy is supplied from the secondary winding 22 of transformer I2DT to the pick-up winding of relay IZFSA.

At this time the holding winding of relay I2FSA is short circuited by back contact 2l of the relay so that the relay is slow to pick up. The relay and transformer are proportioned so that the first impulse of energy supplied to the relay will not pick up the relay contacts. However, on the next or second picked-up period of the track relay contacts the contacts of relay IZFSA pick leased period of the track relay contacts energy is supplied to the relay IZBSA and its contact-s pick up.

On picking up of the track relay after picking up of the contacts of relay I2BSA energy is supplied to relay I2HA over the circuit which is traced from terminal B through front contact I'I ofthe track relay, wire I8, back contact 29 of relay I2HA, front contact 3l] of relay IZBSA, winding of relay I 2HA, and back contact 46 of relay I2TRB to terminal C.

' When relay I2HA picks up, its contact 29 interrupts connection from wire I8 to the relay, while contact 29 establishes a stick circuit to supply energy to relay IZHA as long as relay IZBSA is picked up. l

In addition, when relay I2HA picks up, its contact 3| interrupts connection from wire I8 to the wire leading to the holding winding of 4relay IZF'SA, While contact 3| establishes connection from wire I8 to the wire'over which energy is supplied to the timing unit I2TU.

On continued code following operation of the track relay energy is supplied to the relay I2FSA during the picked-up periods of the track relayand is supplied to the relay I2BSA during the released periods of the track relay. Accordingly, these relays remain picked up and relay IZBSA maintains the circuit of the relay' IZHA.

vOn'picking up of the contacts of relay I'2FSA its contact 44 interrupts the circuit traced above for supplying energy of '75 code frequency to track transformer IITT, and establishes a circuit including back contact 43 of relay I2BSA for supplying steady uncoded energy to section IIT.

As explained in the patent to Allison and Nicholson referredv to above, if the insulated joints separating sections IIT and I 2T are defective, this steady energy will feed across the joints and prevent release of the track relay IZTR so energy is not supplied to relay I2BSA with the result that relays IZBSA and IZHA remain released, while energy is supplied to the holding Winding of relay IZFSA` to keep its contacts picked up.

However, if the insulated joints are intact so that the steady energy does not reach the track relay IZTR, the contacts of this relay will re- "lease at the end of the on period and cause energy to be supplied to therelay I2BSA so that its contact 43 picks up and interrupts the supply of steady energy to track transformer II'I'I.

. When the contacts of relay IZHA pick up, a circuit is established to supply energy of 75M frequency to track transformer IITT. This circuit is traced from terminal BX through contact ISM of the code transmitter, back contact 48 of relay I2HB, backcontact 49 of relay I2K, back contact f yellow lamp.

On picking up of relay I2HA its contacts 34 and 36 interrupt the circuits traced above for lighting the red lamps of signal IZS while energy is now supplied over front contact 34 of relay I2HA and back contact 35 of relay I2J to the upper yellow light of signal I2S, and is supplied over front contact 36 of relay lill-IA, back.

contact 38 of relay I2J, back contact 6I of ren lay I2K, and back contact 60 of relay I2IIB to -the lower red'lamfp of signal I2S. Accordingly.

signal IZS displays its approach indication Aconsisting of a yellow over a red lamp.

Similarly, when the train vacates section I3T the energy supplied to section I2,Tis changed from 75 to 75M code frequency and the relay I-2HB is picked up as hereinafter explained` in detail and causes the signal I2S 'to display its advance approach indication.

The construction of the timing unit IZTU is not a part of my invention but is shown and claimed in application for Letters Patentof the United States Serial No. 452,902 of Carl Volz, led July 30, 1942. This unit includes a transformer having'a primary winding which is energized in multiple with a condenser, while the secondary Winding of the transformer is connected through a rectifier to the winding of relay IZTRB. The various parts of the unit are proportioned so that the energy supplied to the transformer primary winding causes the transformer core to be saturated, while on interruption of the supply of energy to the transformer primary winding, this winding andthe condenser associated therewith form a highly damped os' cillating circuit.Y The energy circulating` in the transformer primary winding causes energy to be induced in the transformer secondary winding from which it is supplied through the rectiflerto the relay IZTRB; The characteristics -oiY the timing unit and of the relay I2TRB are such that on interruption of the supply of energy to the timing unit, energy is supplied therefrom to the relay IZTRB which is effective to cause the contacts of relay I2TRB to pick up and to remain picked up for a time longer than the short off period in the 75M code but not as long as the off periods in the '75A code.

When the track relay IZTR is responding to energy of 75 code frequency, energy is supplied to the primary winding of the transformer of the timing unit I ZTU over the circuit which is On movement of the track relay contacts to their released positions the supply of energy to the timing unit transformer is cut oif, and this unit operates as explained above to supply energy through the rectifier incorporated in the unit to the relay I ZTRB over the circuit which is traced from the positive output terminal of the rectifier over back contact 5S of the track relay and Winding of relay IZTRB to the negative terminal of the rectier. The energy supplied to the winding of relay IZTRB causes the contacts of this relay to pick up and to remain picked up for a short time interval. However, as explained above, this time interval is shorter than the off periods in the rI5 code so that when the' track relay is responding to energy of '75 code frequency, the contacts of relay IZTRB release before the track relay contacts pick up again, and as a result contact 54 of relay IZTRB establishes the circuit for supplying energy to the unit IZTU on subsequent picking up of the track relay contacts.

Inaddition, contact 54 of relay IZTRB interrupts the circuit of relay I2HB so that this relay remains released at this time, and its contact 48 maintains theY circuit for supplying energy of 75M code frequency to section IIT, while its through contact front contact 48 of relay I2HB, back contact 49 contact 60 maintains the circuit of the lower red lamp R of signal I2S.

On picking up of relay IZTRB its contact 46 interrupts the circuit of relayk IZHA, but this relay is sufficiently slow in releasing to remain picked up during the picked-up periods of contact 45.

As the circuit of relay I2HA includes a back contact 46 of relay IZTRB, the relay I ZHA will be released if the contacts of relay IZTRB remain picked Vup4 for any reason. This arrangement checks the relay IZTRB to insure that it releases, and, therefore, permits the' use of a relay having metal contacts for this purpose.

When the` train advances far enough to vacate section I3T, energy of '75 code frequency feeds to the track relay for that section so that signal I3S displays its approach indication, while energy of 75M code frequency is supplied to section I2T. On the supply of this energy to the track relay |2TR it continues to follow code in such manner that the relays IZFSA, IZBSA and I2HA are maintained energized. As explained above, each time the track relay contacts release the contacts of relay IZTRB pick up, While when a short olf period in the 75M code is encountered, the contacts ofthe track relay pick up before the contacts of relay IZTRB release. When this occurs, energy is supplied to relay IZHB over the circuit which is traced from terminal B through front contact I'l of relay IZTR, wire I8, front contact 3l of relay IZHA, back contact 53 of relay IZK, back contact 32'0f relay I2J, front contact 52 of relay IZBSA, front contact 54 of relay I2TRB, and winding of relay I2HB to terminal C.

In addition, when the contacts of the track relay pick up at a time when the contacts of relay IZTRB are picked up, energy is supplied to the relay IZTRB over the circuit which includes its own front contact 58, front contact 56 of relay I2TR, winding of relay IZTRB, and through the rectifier of the timing unit to terminal C. This energy keeps the contacts of relay iZTRB picked up throughout the long on period in the 75M code following the short o period so that con'- tact 54 of relay I2TRB maintains the circuit of relay I2HB and thus insures that energy will be supplied to relay I2HB throughout the long on period in the 75M code.

The relay I 2HB is of a type the contacts of which are slow in releasing, and when the relay is energized throughout the long on period in the '75M code, the flux in the relay core is built up to a value such that the relay contacts Will remain picked up during the intervals between the long on periods in the 75M code.

At this time energy is supplied to relay IZBSA over the circuit which is traced from terminal B through front contact 58 0f relay IZTRB, front contact 25 of relay I2FSA, and winding of relay I2BSA to terminal C. This insures that relay IZBSA will remain picked up throughout the long on periods in the 75M code.

On picking up of the contacts of relay IZHB i its contact 48 interrupts the circuit traced above for supplying energy of '75M code frequency to track transformer I IT'I, and establishes a circuitfor supplying energy of code frequency thereto. This circuit is traced from terminal BX |20 of the code transmitter,

of relay IZK, back contact 40 of relay I2J, front contact 42 of relay IZHA, iront contact 43 of relay IZBSA, front contact 44 of relay IZFSA,

and primary winding Vof the track transformer I ITT to terminalzCX.. f When relay IZHB picks up, its contact 60 interrupts the previously traced circuit for supply-` ing. energy to the lower red lamp R of signal I2S and establishes a circuit for supplying energy to the lower yellow lampY of this signal. This circuit is. traced from terminal B through front contact 3E.of relay IZHA, back contact 38 of relay I2J, back contact 6l of relay 12K, front contact 60 of relay I2HB, `and lamp Y to terminal C. Accordingly, the signal I2S displays its,v advance approach indicationlconsisting of a yellow lamp over a yellow lamp. Y

.f On release of track relay IZTR after the long .on period in the 75M code its contact l1 interrupts the supply of energy to `relay l2HB,'while contact 56 of the track relay interrupts the stick circuit of the relay IZTRB'so that its contact 58 releases and additionallyA interrupts the stick circuit of relaylZTRB and also interrupts the cir-- cuit traced above for supplying energy to relayv IZBSA. At this time, however, relay IZBSA is energized by current supplied over back contactv I1 of relay IZ'I'R.

On release of vcontact 54 of relay IZTRB the relay IZTRB is connected to the timing unit, but during the previously` picked-up period of the track relay the contact 54 of relay I2TRB interrupted the vcircuit for supplying energy to the primary ,winding of the transformer incorporated in the timing unit I2TU so that no flux is present in the transformer core, and on release of the track relay contacts there is no change in energization of the transformer primary winding. Accordingly, no energy is available from this unit, and no energy is supplied to the relay rIZTRB over the circuit established by back contact 56 of the track relay, and the contacts of relay l ZTRB remain released.

On the f irstpicked-up period of the track relay contactsaiter the long on period in the '15M code energy is supplied to the primary winding of the transformer incorporated in the timing unit IZTU over the circuit including back contact -54 of relay IZTRB so that on the next released perioddof the track relay contacts the timing unit I2TU operates as explained above to supply energy tothe relay I2TRB and its contacts become pickedup. However, the onf period in the 75Mvcode at this time is longer than the release period of the contacts of relay I2TRB so that its contacts release before the track relay contacts pick up again. Accordingly, energy is not supplied to the relay IZHB at this time.

On the next or second pickedup period of the track relay contacts subsequent to the long on period energy is again supplied to the timing unit I2TU, while on the next released period of the track relay contacts, which occurs dur-ing a short olf period in the 75M code, energy is again supplied fromk 'the timing unit ZTU to the relay |2TRB and its contacts pick up with the result that on picking up of the track relay contacts the contacts of relay IZTRB are still picked up so that energy is supplied over front contact 58 of relay IZTRB to relays |2BSA and ZTRB, while energy is supplied over front contact-54 of relay IETRB to relay I2HB.

It willbe seen, therefore, that when the track relay is responding to energy of 75M code frequency and the short olf period in the code is encountered, the track relay contacts pick up before .the contacts of relayV IZTRB release, and as a result' energy is supplied to relayl IZTRB to maintain itscontacts picked up during the long fon period which follows the short off period.- In addition, energy is supplied to the relay |2I-D3 to pick up its contacts and to maintain them picked up during the time intervals between the long .on periods in the code, While energy is supplied to the relay IZBSA'to maintainitscontacts picked up during the long on period in thiscode. Accordingly, as long as the track relay I2TR responds to energyV of 75M code frequency the contacts tof relay IZHB are maintained pickedup.:

l It will. be. seen also that the apparatus is arranged so that energy is'supplied to the relays iEHB and IZBSA over separate and` independent circuits-so. that the energy supplied to the relay IZHB is not limited in value due to the resistance of the winding .of relay IZBSA. As energy is suppliedtocrelay IZHBover anfindependent circuit, the energy supplied to relay I2HB during 4the long on'periods in the-75M code may be high enoughinvalue..tobuild up sufficientl ilux .inthe relay core .to .insure that the, relay contacts will remain picked up throughout the intervals vbetween long on periods in the '75M code.: r. l l When-the train advances far enough to vacate the section in advance of section 13T, energy of .75M code frequency is supplied to section |3T and ythe equipment forv that section operates as explainedabove in connection with section |2T to cause energy of 120 code frequency tobe supplied to the rails of section I2T. When the track relay IETR responds to this energy, the frequency ofthe current inducedin the secondary winding 23 of decoding transformer I2DT is-such that it is freely passed by resonant vunit I2ODU and the relay |2K picks up so that Contact 53 interrupts the circuit for supplying energy to the timing unit LITU, and forV supplying energy to relay IZTRB and` to relay l2I-IB. As vthe supply-of energy to the timing unit is cut off energy will not thereafter be Asupplied from the timing unitA I2TU tothe relay IZTRB and its contacts will remain released and contact 58 will- Vnot establish the circuits for supplying energy to relays IZTRB and I2BSA. vvAccordingly, relays IZHB and .I ZTRB thereafter 4remain released, while relay IZBSA is controlled solely by the track relay. When-energy of or 180 code frequency is supplied to the ltrack relay, the equipment operates in substantially the same manner as the equipment shown in application for Letters Patent of -theUnited States Serial No. 452,894 of Frank `I-I. Nicholson and Crawford E. Staples.

Thissystem operates insubstantially the same manner -as that shown V-in the application of Nicholsonand Staples videntified above, to cause the lockoutv circuitwto be established in the event an insulated :joint separating two sectionsA breaks .downr'as av result of passage of a train through the-track lstretch. i This! system is also arrangedso that, except when the equipment is responding to energy of' 15M code frequency, the release time of the reY lay'BSA is. not increased.y This insures prompt establishment of the' lockout -circuit iff an insulated joint breaks `down when the section isy vacant, while it insures Vprompt display of stop indication by the'associated signal if for any reason steadyenergy is supplied to a section.'

-When vthe track section isvacant, `energyof appropriate code frequency isv supplied to section I2T, and ,relays IZFSA, IZBSAjand' ZHA are f picked up,A` -Whilel one Vof the relays IZHB,

I2K and I2J may be picked up. Under these conditions energy of suitable code frequency is supplied to section I IT over the circuit which includes front contacts of relays yIZFSA, IZBSA and I2HA.

If an insulated joint 3 separating sections HT and I2T becomes defective so that coded energy supplied to section HT feeds across the insulated joints, it will combine with the energy supplied from transformer I2'IT to the track relay IZTR. If at the time the insulated joint becomes defective the impulses of energy supplied from transformers llTT and I2TT are out of step, the contacts of track relay I2TR. will be held picked up an abnormally llarge proportion of the time. If at the time the insulated joint becomes defective, the impulses of coded energy supplied from the transformers HTT and I2TT are in step they will soon become out of step as the code transmitters controlling the supply of energy to the two sections are operated by induction motors and these will not run at exactly the same speed for any substantial period of time.

As a result of the increase in the picked-up periods of the track relay contacts, the circuit of the relay I2BSA is interrupted so much of the time that this relay will release with the result thatrits contact 43 interrupts the circuit for supplying coded energy to the transformer IITT and establishes the circuit for supplying steady energy thereto.

The circuit for supplying energy to relay IEBSA includes back contact I1 of the track relay IZTR and front contact 26 of relay IZFSA, while when Contact 26 of relay IZFSA is .picked up, a snubbing circuit including resistor 28 is established for relay IZBSA.

When the track relay contacts pick up, contact ll interrupts the circuit of relay |2BSA and the flux in the relay core collapses and induces energy in the relay winding. This energy may flow through the circuit provided by resistor 28 so that collapse of the flux in the relay core is delayed with the result that release of the relay contacts is delayed. Y

The resistance 28 is of such value that release of the contacts of relay l2BSA is delayed slightly longer than the longest on periods in the normal code supplied to relay IZTR, that is, slightly longer than the on periods in the '75 code. This insures that the supply of coded energy to the section in the rear will not be interrupted when the track relay IZTR is responding to coded energy of normal pattern, while it insures prompt interruption in the supply of coded energy to the section in the rear if the contacts of the track relay are picked up an abnormally large part of the time, as occurs when an insulated joint breaks down when the stretch is vacant.

If the resistance of the snubbing Vcircuit for the relay IZBSA is reduced substantially below the Value determined by the resistance 28, the release time of the relay Vwill be increased and the relay will be less sensitive to increases in the picked-up periods of the track relay and will be less prompt in establishing the lockout circuit.

This system is arranged so that although the windings of the relays I2BSA and IZTRB are connected in series when the contacts of the track relay are picked up, the resistance of the snubbing circuit for relay VI2BSA is not materially reduced.

Referring to the drawing, it Will be seen that when the contacts of the track relay Sand' of relay IZFSA are picked up, the-left-handfterminal of the winding of relay 12BSA is connected over front contact 26 of relay IZFSA and front contact 56 of relay I2TR to the left-hand terminal of the relay IZTRB. The right-hand terminal of the Winding of relay IZBSA is 'connected to terminal C` of the source Aof current, while the right-hand terminal of relay |2TRB yis connected through the rectifier of the timing unit to terminal C so that there is a circuit between the two terminals of the winding of relay .IZBSA through the winding of relay .IZTRB and the rectifier of the timing unit.

When the track Arelay contacts are released, energy is supplied to .the relay I2BSA and cur rent flows through the relay winding from its leithand to its right-hand terminal. When the track relay contacts pick up, the supply of energy to the winding of relay I2BSA is interrupted, while on .the resultant collapse of the iiux .in the relay core energy is induced in the relay winding so that a current .'-ows in the same direction as the current previously applied through the relay. Some of this .current will ow through the snubbingresistor 28 and serves to delay release of the relay contacts. AThe "current induced -in the winding of relay |2BSA-als0 tends to flow to terminal C of the source and therefrom through the rectifier of the timing unit, through the winding of relay I2TRB, and over front contact 56 of the track relay andiront contact 26 of relay IZFSA tothe left-hand terminal of relay IZBSA.

However., the rectifier of the timing unit is included in the circuit just Ytraced iin `such mani ner that current flows through the rectifler in its high resistance or reverse direction. This is true since the positive Voutput Vterminal of the rectifier of the timing unit is vconnect-eel `to 'terminal C of the source. The rectier has such high resistance to flow of current therethrough in the reverse direction that very little energy will flow through the snubbing circuit which includes the rectifier and the winding of relay I2TRB. Accordingly, the release time of the relay I2BSA is determined by the value of the snubbing resistor 28 and this resistor may -be selected to cause the relay -I2BSA tohave appropriate releasing characteristics.

Although I Vhave herein shown and described only one form of railway signaling system embodying my invention, it is understood that var'- ious changes and modications may -be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus kdescribed 'my invention, what I claim is: v

1. In a railway signaling system, in ycombina'- tion, a section of railway track,a code following track relay energized by current supplied over the rails of said section, means for supplying to the section rails recurring cycles -of coded energy each consisting of an on and an off" period of substantially equal duration, meansfor at times periodically modifying the cycles of codedenergy supplied to the section rails by substantially reducing the length of the ofi `pe-r riod in a code cycle, a first, second, third and fourth auxiliary relay,` a timing unit eiective on interruption of the supply of energy thereto to supply energy effective to maintain the third auxiliary relay picked up fora vtime longer 4than anV foff period of reduced length but .shorter amaca than an foff period of normallength a circuit including a front contact of said track relay for supplying 'energy'to the rst` auxiliary relay,A a circuit including a back contact of the` track relay and a front contact of said first auxiliary relay for lsupplying energy to the secondl auxiliary relay, a circuitincluding front contacts of the track relay and of said second auxiliaryrelay for supplying energy to said timing unit, a circuit including ia' back contact-cf` said track relay for supplying `energy from ,said timing unit through a rectier to said 'third auxiliary relay, a circuit includinglfront l'contactsof said track relay and said third auxiliaryrelay for supplying energy to said fourth auxiliary relay, a contact of said third auxiliary "relay being effective when picked'up to establish a circuit including a front contact of Vsaid rst auxiliary relay for lsupplying energy to the,v second auxiliary relay and to also establish a circuit: including a front 'contactof the track relay Yand vincluding in Series therewith' the rectifier associated' Iwith said tim:- ing unit for supplying energy tothethird auxiliary relay, andfrneans governed by'said first,` second and fourthL auxiliary relays'for supplying energy to the'rails of the adjacent section in Vthe rear.

2. In a railway signaling syste'm,"-in combination, a section of railway track, a codefollowing track relayenergized by current supplied over the rails of said section and provided with-first, second, third and fourth movable contacts, means for supplying to the section rails recurring cycles of coded-energy each-consistingof an-on and an off period of substantially equal duration, means for at times periodically-modifying the cycles of coded energy supplied to the section rails by substantiallyreducing the length of the-off period in a code cycle, a first, second, third and fourth auxiliary relay, a `timing'unit effective on interruption of the supply of energy thereto-to supply energy effective `tofmaintain the third auxiliary relay lpicked up for a time longer than lan off period of -reduced length but shorter than an olf period of normal length,means respon'- sive to code following operation of the track relay and includingtherst and second track relay contacts for supplying energy toa said first auxiliary relay, a circuit including afront contact of the first auxiliary relay and the back .contact of the trackrelay ,third movable contact for suplplying energy tothe-/second auxiliary relay; a circuit includingl a front contact of said second auxiliary relay and the frontfcontact `of the track relaythird movable .contact for supplyingienergy to said timing unit, laV circuit including fthe .back Contact ofthe track relay fourth-movable Contact for supplying energy from said.. timing unit through. a rectiiierto said third auxiliary relay, a circuit including the front. contact ofthe track relay thirdmovable contact anda front contact of said third auxiliary relay for supplying energy to saidfourth auxiliaryrrelay,-,a circuit includingfront contacts of said rst and third auxiliary relaysffor supplying,v energyto said second auxiliary -relay, a circuit including a front contact ofmsaid thirdauxiliary relay and the frontcontact of the track relay fourthmovable Contact for supplying venergy to saidthirdi auxiliary relay, 4and means vgoverned bysaid first, second and fourthauxiliary relays ,for supplying energy to the rails-of the adjacent section,r in therear. Y z' l In a railway A signaling system, in combination, a section; of railway-tracka code following track relay energized'bycurrent supplied over the rails ofsaid section and provided with first, second, third and fourth movable contacts, means for supplying tothe section rails recurring cycles of coded energy each consisting of an on and an off period of substantially equal duration, means for at times periodically modifying the cycles of coded energy supplied to the section rails =by substantially reducing the length of the oif.period in a code cycle, a first, second, third and fourth auxiliary relay, a timing unit effective on interruption of the supply of energy thereto to supply energy-effective to maintainthe third* auxiliary relay picked up for a time longer than an olf period of reduced length` but shorter than an off period of normal length, means responsive to code following operation of the track relay and including the first and second track relay contacts for supplying energy to said first auxiliary relay, a circuit including a front contact of the first auxiliary relay and the back contact of the track relaythird movable'Contact` for supplying energy to the second auxiliary re-` lay, a circuit including a front contact of said second-auxiliary relay and the front contactl of the track relay third movable'contact for supplying energy to said-timing unit, a circuit including the back contact of the track relay fourth movable contact for supplying energy from said timing unit through a rectifier to said third auxiliary relay, a circuit including the front Contact of the track relay third movable contact and l front contacts ofsaid second and thirdl auxiliary relays for supplying energy to said fourth auxiliary relay, a circuit including front Vcontacts of said first and third auxiliary relays for supplying energy to said second auxiliary relay, a circuit including a front contact of said third'aux-iy iliary relay and the front contact of jtheltrack relay fourth movable Contact for supplying energy to said third auxiliary relay, and means governedby said first, seco-nd and fourth auxiliary' relays for supplying energy to the rails of the adjacent section in the'rear.

4. In a railway signaling system, in combination, a section of railway track, a code following track relay energized by current supplied over the rails of said section and provided with first, second, third and fourth movable contacts, means for supplying to the section rails recurring cycles of coded energy each consisting of an on and an off period of substantially equal duration, means for attimes periodically modifying thel cycles of'coded energy supplied to the sectionirails bysubstantially reducing the length of theoif period in a' code cycle, a first, seconcl,'third and fourth auxiliary relay, aftiming unit effective' on interruption of the supply of energy thereto lto supply energy effective to maintain the third auxiliary relay picked up for a time longer than anfoff period of reduced length but shorter than an off period of normal length, means responsive to code following operation of the track relay and including the first and second track relay contacts for supplying energy to said first auxiliary relay, a circuit including a front contact of the first auxiliary relay and the back contact of the track relay third movable contact for supplying energy to the second auxiliary relay,

va circuit including a front contact of said second' auxiliary relay and the front contact of the track relay third movable contact for supplying energy to. saidvjtimingunit, a circuit including the back contactof thetrack relay fourth movable contactfor supplyingjenergy from said timing unit through a rectifier to said third auxiliary relay, a circuit including the front contact of the track relay third movable contact and a front. contact of said third auxiliary relay for supplyingenergy to said fourth auxiliary relay, a circuit including front contacts of said rst and third auxiliary relays for supplying energy to said second auxiliary relay, a circuit including a front Contact of said third auxiliary relay and the front contact of the track relay fourth movable contact for supplying energy throughtherectifier associated with said timing unit to said third auxiliary relay, and means governed by said first, second and fourth auxiliary relays for supplying energy to therails of the adjacent section in the rear.

5. In a railway signaling system, in'cornbination, a section of railway track, a code following track relay energized by current supplied over the rails of said section and provided with first, second, third and fourth movable contacts, means for supplying to the section rails recurring cycles of coded energy each consisting of an ,on and an o ii, period of substantially equal duration, means for at times periodically modifying the cycles of coded energy supplied to the section rails by substantially reducing the length ofthe off period in a code cycle, a rst, second, third, fourth and fifth auxiliary relay, a timing unit effective on interruption of the supply of energy thereto to supply energy effective to maintain thelfourth auxiliary relay picked up for a time longer than an off period of reduced length but shorter than an off period of normal length, means responsive to code following operation of to said rst auxiliary relay, a circuit including a front contact of the first auxiliary relay and the back contact of the track relay third movable contact for supplying energy to the second auxiliary relay, a supply Wire to which connection is established from one terminal of a source of current over the front contact of the track relay third movable contact, means including a back contact of said third auxiliary relay and a front contact of said second auxiliary relay for establishing connection from said supply wire to the winding of the third auxiliary relay, means including front contacts of said second and third auxiliary relays for supplying energy to said third auxiliary relay, means including front contacts ofv said second and third auxiliary relays for establishing connection from said supply wire to saidtirning unit, a circuit including the back con-V tact of the track relay fourth movable contact` for supplying energy from said timing unit through a rectifier to said fourth auxilary relay, means including front contacts of the second, third and fourth auxiliary relays for establishing connection from said supply wire to the fifth aux-- iliary relay, a circuit including front contacts of; the fourth and first auxiliary relays for supplying energy to the second auxiliary relay, aA circuit; including a front contact of the fourth auxiliary relay and the front contact of the track relay fourth movable contact for supplying energyito the fourth auxiliary relay, and means governed by said first, second, third and fth auxiliary relays for supplying energy to the rails of the adjacent section in the rear. 6. In a railway signaling systeinfincombi nation, a section of railway track, a code followingV track relay energized by current supplied over the rails of said section and provided with first, second, third and fourth movablecontacts, means for supplying tothe section rails recurring cycles of coded energy each consisting of an on" and an ofP period of substantially equal duration,- means for at times periodically modifying the cycles of coded energy supplied to the section rails by substantially reducing the length of the off period in a code cycle, a first, second, third and fourth auxiliary relay, a timing unit effective on interruption of the supply'of energy thereto to supply energy effective to maintain the third auxiliary relay picked Aup for a time longer than an off period of reduced length but shorter than an ofi period of normal length, means responsiveV to Vcode following operation of the track relay and including the first and second track relay contacts for supplying energy to said first auxiliary relay, a circuit including a front contact of the first auxiliary'relay and the back contact of one of the track relay movable contacts vfor supplying energy to lthe second auxiliary relay, a circuit including a front contact of said second Aauxiliary relay and the front contact of the'track relay third movable contact for supplying energy to said timing unit, a circuit including the back contact of the track relay fourth movable contact for supplying energy from said timing unit through a rectifier to said third auxiliary relay, a circuit including the front Contact of the track relay third movable contact and a front contact of said third auxiliary relay for supplying energy to said fourth auxiliary relay, a circuit including front contacts of said first and third auxiliary relays for supplying enthe track relay and including the mst and sec 3 j ergy to said second auxiliary relay, a. circuit inond track relay contacts for supplying energy cluding a front contact of said third auxiliary relay and the front contact of the track relay fourth movable contact for supplying energy to said third auxiliary relay, and means gov- -erned lby said first, second and fourth auxiliary relays for supplying energy to the rails of the adjacent section in the rear. y

7. In a railway signaling system, in combination, a section of railway track, a code following track relay yenergized by current supplied over the rails of said section and provided with first, second, third and fourth movable contacts, means for supplying to the section rails recurring cycles of coded energy each consisting of an on and an off period of substantially equal duration, means for at times periodically modifying the cycles of coded energy supplied to the section railsl by substantially reducing the length of the off period in a code cycle, a first, second, third, vfourth and .fifth auxiliary relay, a timing unit effective on interruption of the supply of energy thereto to supply energy effective to maintain the .fourth auxiliary relay picked up for a time longer than an off period of reduced lengtlibut shorter than an o period of normal length, means responsive to code following operation of the track relay and including the first and second track relay contacts for supplying energy to said first auxiliary'relay, a circuit including a front contact of the first auxiliary relay and the back Vcontact of one of the track relay movable contacts for supplying energy to the second auxiliary relay, a supply wire to which connection is established from one terminal of a source of current over the front contact of the ktrack relay third movable contact, means including a back contact of said third auxiliary relay and a front contact of said second auxiliary relay for establishing connection from said -supply Wire to the winding of the third aux-- timing unit, a circuit including the back contact of the track relay fourth movable contact for supplying energy from said timing unit through a rectier to said fourth auxiliary relay, means including front contacts of the second, third and fourth auxiliary relays for establishing connection from said supply Wire to the iith auxiliary relay, a circuit including front contacts of the fourth and iirst auxiliary relays for supplying energy to the second auxiliary relay, a circuit including a front contact of the fourth auxiliary relay and the iront contact of the track relay fourth movable contact for supplying energy to the fourth .auxiliary relay, and means governed by said rst, second, third and fourth auxiliary relays for supplying energy to the rails of the adjacent section in the rear.

8. In a coded railway signaling system, in combination, a section of railway track, a ycode following track relay energized by current supplied over the rails of said section and provided with a plurality of movable contacts, means for supplying to the section rails recurring cycles of coded energy each consisting of an on and an off period of substantially equal duration, means for at times periodically modifying the cycles of coded energy supplied to the section rails by substantially reducing the length of the oi period in a code cycle, a rst, a second, a third, and .a fourth auxiliary relay, a timing unit effective on interruption of the supply of energy thereto to supply to the input terminals of a rectier energy effective t0 maintain the third auxiliary relay picked up for a time longer than an off period of reduced length but shorter than an 01T period of normal length, one output terminal of said rectifier being connected to one terminal of the winding of said third auxiliary relay, the other output terminal of said rectifier being connected to a terminal of a source of current and to one terminal of the winding of said second auxiliary relay, a contact of said third auxiliary relay being effective when picked up to connect the other terminal of said source of current over a front contact of the iirst auxiliary relay to the other terminal of the winding of the second auxiliary relay, a movable contact of said track relay being effective when released to connect the other terminal of the Winding of said third auxiliary relay to said other output terminal of said rectifier and being effective when picked up to connect said other terminal of the winding of said third auxiliary relay to Said other terminal of the Winding of said second auxiliary relay, a circuit including another front contact of said track relay for supplying energy to the timing unit provided a movable contact of said third auxiliary relay is released and for supplying energy t0 said fourth auxiliary relay provided said movable contact of said third auxiliary relay is picked up, circuits governed by other contacts of the track relay for supplying energy to the first auxiliary relay when the track relay contacts are picked up and for supplying energy to the second auxiliary relay when the track relay contacts are released provided the contacts of the first auxiliary relay are picked up, and means governed by the rst, second and fourth auxiliary relays for supplying energy to the rails of the adjacent section in the rear.

ANDREW HUFNAGEL. 

